ABC(LOS ANGELES) — Actor, host and ABC’S Good Morning America contributor Cameron Mathison revealed on the show Wednesday that doctors have found a 4.2 centimeter mass on his right kidney.

In a new interview with GMA, Mathison spoke about how the tumor could have been growing for 10 years or more inside his kidney. He also told fans via Instagram. “The mass is consistent with renal cell carcinoma, or kidney cancer.”

When he got the news, Cameron said he thought he was in a dream, and tried to wake up.

“I called my wife,” he said of the first thing he did after getting his diagnosis. “First thing out of her mouth, which is amazing to me is, ‘We got this, we’re going to beat it.'”

The scan results came after years of abdominal pain and doctor visits trying to figure out what was wrong. He now urges everyone to take control of their health.

“I don’t drink, eat incredibly healthy, I eat a very low sugar, low carbohydrate diet typically,” he explained. “Things that likely, in our best guess, have helped keep [the mass] from spreading, and growing even quicker.”

Mathison is set to have surgery Thursday to remove the mass or, possibly, the entire kidney.

After the interview, Dr. Jennifer Ashton said that when it comes to cases like Mathison’s, “Always trust your body.”

While insurance and costs might make it hard for a doctor to send you for an MRI or another test right away, no one knows your body better than you.